This R34 Clinical Trial Planning grant application is to support the organization of a phase II randomized trial. We propose to conduct a single center (Rochester) randomized, double-blind placebo-controlled Phase II trial (RCT) to evaluate the preliminary efficacy of topical PI given to children with S-ECC (Severe-Early Childhood Caries) who have been surgically treated in one session. All participants will be followed for 2 years or until relapse, whichever is sooner. Participants, largely drawn from the minority community, will be randomized to one of 2 interventions (N=140): 1) topical PI 4 times/year plus the community standard of care as defined by the ADA (fluoride varnish (FV) 4 times/year +OHI+ counseling regarding decay promoting feeding behaviors or 2) topical placebo 4 times/year plus the community standard of care. The outcome measure will be carious lesions with dentin involvement (Code 5, International Caries Assessment and Detection System (IDCAS). Early Childhood Caries, (ECC) is a growing public health problem that afflicts young children most often in lower socioeconomic groups. S-ECC is the most damaging form of ECC and has reached near epidemic proportions worldwide. S-ECC is characterized by an overwhelming infectious challenge by mutans streptococci (MS) and decay promoting feeding behaviors. The standard of care for S-ECC includes restoration and extraction of carious teeth, application of topical fluoride, oral hygiene instructions (OHI) and recommendations regarding feeding behaviors (Oral Health Policies, Reference Manual, Amer Acad of Pediatr Dent, 2005). Dental surgery has minimal impact on oral MS reservoirs and counseling regarding feeding habits has had very limited success. Not surprisingly, clinical outcomes for treatment of S-ECC are poor; earlier clinical outcomes studies demonstrate that approximately 40% of children treated for S-ECC will develop new carious lesions within 1 year post dental surgery. Recently, the ADA recommended fluoride varnish (FV) at least twice per year and ideally 4 times per year for children with S-ECC; however, recent papers demonstrate clearly than even multiple and intensive fluoride treatments do not arrest tooth decay in high risk populations and such children continue to experience extensive new decay,. Improved clinical outcomes for S-ECC will likely be realized through treatment modalities that are not a financial burden on health resources and focus on the infectious aspect of this disease. Suppressing oral MS reservoirs with a topical anti-microbial agent is a potential approach. In this regard, 10% povidone iodine (PI) is approved for pediatric oral use and has suppressive effects on oral MS reservoirs in the setting of S-ECC. The significance of the proposal's design is twofold: 1) it will generate data on the prevalence and incidence of new caries lesions in children treated for S- ECC receiving quarterly treatment with FV, which will be valuable for planning a Phase III trial and 2) it will fill an important gap in our knowledge on the efficacy of FV alone and in combination with PI for high caries risk children. PUBLIC HEALTH RELEVANCE: Severe Early Childhood Caries (S-ECC) is an infectious disease that continues to be a significant global public health problem that afflicts young children most often in lower socioeconomic groups and has reached epidemic proportions. Clinical results for treatment of S-ECC are poor; approximately 40% of children treated for S-ECC will develop new cavities within 12 months after dental surgery. Improved clinical outcomes for S- ECC will likely be realized through interventions that are not a financial burden on health resources. This proposal will assess the efficacy of a combined therapy using an antiseptic and a fluoride varnish for improving clinical outcomes for S-ECC.